Diesel Cars Found To Be Emitting Another Dangerous Pollutant

2594 Diesel Cars Found To Be Emitting Another Dangerous Pollutant
A new study documents a "hidden" pollutant belched out by diesel cars. Kichigin/Shutterstock

It has not been a good week for diesel cars. First the shocking revelation about Volkswagen rigging the emissions tests for their diesel-powered vehicles in the United States, and suspicions that this might not be limited to the U.S., but is an industry-wide practice. Now, new research has revealed that diesel cars are belching out another little-known pollutant at dangerous levels.

According to the new study, this “hidden” by-product contributes to both ozone and particulate matter. These are known to be some of the worst air pollutants due to the damage they do to both the atmosphere and human health. And diesel engines are pumping them out up to a staggering 70 times higher than the levels expected by the government.


“It's definitely been hidden until now,” Dr. Jacqueline Hamilton, who led the study published in Atmospheric Chemistry and Physics, told BBC News. “What we found is that there's actually a lot of this unburned material from diesel that we haven't seen before. That might be having a bigger impact on ozone and particle formation than petrol cars are, and historically no one has looked at these emissions at all.”

The unburnt materials of which Dr. Hamilton talks are actually long-chain hydrocarbons that escape out the back of the vehicles. Hydrocarbons are the organic compounds made up of a chain of carbon atoms with hydrogen attached, which form the basis of the fuel. Traditionally, attention has been focused on those hydrocarbons with only two to seven carbon chains, simply because they’re easy to test for. But by using more sophisticated measuring technology, the researchers from the University of York have been able to detect these longer forms in the London air.

They found that these long-chain hydrocarbons contribute up to 50% of the ozone production potential in London during winter, and while this dropped to around 25% in summer, they are probably having a major impact on our health. The level detected in the air, they found, was far higher than the data given by the car manufacturers to the government.

“If you look in the real atmosphere, compared to the test data, there's a lot of [nitrogen oxide] and a lot of these hydrocarbons as well,” says Dr. Hamilton. “Volkswagen have admitted they have deliberately turned off the emissions controls, and if these controls lower emissions of hydrocarbons, if you just turn that off, you are definitely gaming the system.”


This new study comes as the scandal involving Volkswagen widens even further. Last week, it was revealed that the German car manufacturer had been cheating the emissions tests in the U.S. They did this by installing a piece of software in the vehicles that could detect when they were being tested, and then lower the amount of nitrogen oxide that the car emitted. The result was that in the real world, these cars were actually pumping out up to 40 times the legal limit of the pollutant.


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  • diesel,

  • air pollution,

  • emissions,

  • Volkswagen,

  • nitrogen oxide,

  • deception